<html>
<body>
  <div style="width: 10px; height: 10px;" id="dirty"></div>
</body>
<script type="text/javascript" charset="utf-8">
  setInterval(function(){
    document.getElementById('dirty').style.backgroundColor =
      '#'+(Math.random()*0xFFFFFF<<0).toString(16)
  }, 10)
</script>
</html>
